Aguirre said he also received information that drugs are being cooked inside hidden underground tunnels at the NBP.

The Department of Justice has received offers of technological aid to search for the tunnels.

Since 2015, the government has tried to suppress irregularities like the narcotics trade and the luxurious lifestyle of high-profile inmates inside the country's largest prison facility.

Numerous raids under Oplan Galugad, however, failed to stem the flow of contraband items at the NBP.

President Rodrigo Duterte himself blamed the alleged corruption of the Bureau of Correction (BuCor) for the persistent problem, saying some prison guards accept bribes from detainees in exchange for allowing illegal activities.

Duterte also said drug lords were still able to continue with their illegal activities even while inside the state penitentiary.

Elite policemen from the Special Action Forces (SAF) on Wednesday replaced jail guards in a bid to stamp out the alleged corruption at the NBP.